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Voyagers to the Outer Planets
Volume 31 - Saturn
Images in Range 35363.06 - 35629.19 in Compressed Format
Images in Range 35363.06 - 35629.19 in Browse Format
This Compact Disk-Read Only Memory (CD-ROM) volume is one of the set of
volumes containing all images taken by NASA's twin Voyager spacecraft
during their encounters with the planet Saturn.
The set of volumes which comprise the complete Saturn image data set
begins with volume 26 of the "Voyagers to the Outer Planets" collection and
proceeds chronologically through the data set. The earlier volumes in
the collection contain:
a complete Uranus image data set (volumes 1-3)
a set of selected Saturn images (volumes 4-5)
a set of selected Jupiter images (volumes 6-8)
a complete Neptune image data set (volumes 9-12)
a complete Jupiter image data set (volumes 13-25)
The images on volumes 4-5 (selected image data) will be repeated somewhere
on the complete image data set volumes. The image data will be unchanged,
but corrections may have been made to descriptive information (in the
label or the Index Table) such as TARGET or NOTE. In the case of corrected
TARGET values, a repeated image may show up in a different directory than
it did on volumes 4-5.
The images are full resolution (800 pixels by 800 scan lines) digital
images returned by the Voyager cameras. No additional processing
has been performed to enhance the images. The images are compressed to
permit us to pack more data onto each volume, but the images can be
restored to their full resolution using algorithms described in documentation
on this disk. Image decompression software in several programming
languages is also included on the disk.
Sub-sampled "Browse" images consist of every fourth pixel of every
fourth scan line, producing an image of 200 pixels by 200 scan lines.
Browse images allow rapid location of images of interest, prior to
retrieving and decompressing the compressed version of the image to
get the full 800 pixel by 800 scan line resolution.
Only a few files, including this one, are located in this volume's main
directory. The file VOLDESC.SFD contains general information similar to
what is in this file but in a format that is easier for computer programs
to access. Volumes 25 and 38 contain a file called ERRATA.TXT, which
documents all the errors found in both text and image files on CD volumes
13 - 25 and 26 - 38 respectively. All other files are located in
directories below the main directory.
The directory named DOCUMENT contains a document file named VOLINFO.TXT that
describes in detail the organization of this disk, as well as the format and
content of the Voyager images. It is highly recommended that the VOLINFO
document be read before trying to process image files. Also in the DOCUMENT
directory is a file called ANOMALY.TXT which describes both missing data and
known anomalies. Volumes 25 and 38 also contain a cumulative anomaly file
called CUMANOM.TXT. This file documents the inconsistencies on volumes 13
- 25 and 26 - 38, respectively.
The directory named INDEX contains a file IMGINDEX.TAB which is an index
to the images on this volume. The index table is human and machine readable.
While you can locate images by simply searching through the index yourself,
the table has been designed so that it can be easily loaded into most
database managers for fast and efficient searching. The file named
INDXINFO.TXT in the INDEX directory describes the index table in detail.
Volumes 25 and 38 also contain a file, CUMINDEX.TAB, containing the complete
set of images on the Jupiter and Saturn CDs respectively.
The directory named SOFTWARE contains source and executable versions of
image decompression software written in FORTRAN, C and VAX Macro assembly
language. There are executable decompression programs for use with
Macintosh, IBM PC, UNIX and VAX/VMS systems. The file named SOFTINFO.TXT in
the SOFTWARE directory briefly describes the software. More detailed
information is found in the .TXT files stored with the software modules
in the MAC, PC, UNIX and VAX subdirectories.
The compressed image files are contained in directories named after the
principal target of the image. The image directories present on this
Saturn volume are:
SATURN - Images of Saturn
CALIB - Unshuttered images in the DARK subdirectory
If there are more than about 100 images of a target on a volume, the images
are further divided into subdirectories based upon their image number.
Each image subdirectory has a name of the form CnnnnXXX, where nnnn are
the first four digits of the seven-digit image number. All images of
the target with image numbers that have those first four digits
will appear in the subdirectory. See the document VOLINFO.TXT for
further information about image numbers.
The Browse image files are arranged into directories using the scheme
outlined above for compressed images. The only difference is that all of
the Browse image directories are located under the directory named BROWSE.
Within the BROWSE directory for example, is a subdirectory named TITAN
that contains all of the Browse format images of the satellite TITAN.
Most files on this disk have a label encoded in the Object Description
Language (ODL). A file's ODL label is readable by both humans and
computers, and it provides a formal description of the format and
content of the file. For most files the ODL label appears at the
beginning of the file (this is the case for the file that you are
currently reading). All image files have such an embedded ODL label
preceding the data in the file. For files where labels can't be easily
included, a separate label file is provided that contains the ODL label
and a pointer to the file that the label describes. These external
label files all have a .LBL file extensions. An example of an external
label is the file IMGINDEX.LBL in the INDEX directory which contains
the ODL label for the index file IMGINDEX.TAB. The LABEL directory
contains two files with external ODL labels that describe the format
and content of the engineering information that is contained within
each image file. The Object Description Language is described in
the document file VOLINFO.TXT in the DOCUMENT directory.